Zeolitic imidazolate framework-8 (ZIF-8)/semiconductor nanocomposites were synthesized by a simple method. The nanocomposites were composed of the in situ grown ZIF-8 and supported ZnIn-layered double oxides (ZnIn-LDOs), in which ZnIn-LDOs were used as a Zn2+ source to form ZIF-8. The ZnIn-LDOs were formed by calcining the microhydrothermally synthesized ZnIn-layered double hydroxide precursor. The effect of the ZIF-8 amount on the morphology and photocatalytic activity of nanocomposites was studied. The nanocomposites were composed of the aggregation of ZIF-8 in the shape of a dodecahedron and ZnIn-LDOs in the shape of a flower. The ZI-1-ZIF-8 exhibited excellent photodegradation activity, in which the degradation rate of methylene blue (MB) was 97% under 120 min simulated sunlight irradiation. Moreover, the photocatalytic degradation activity could still be maintained at 95% after five runs. The trapping experiment indicated that the reactive radicals of center dot OH play an important role in MB removal. Similarly, the experimental results showed that ZIF-8/ZnIn-LDOs could degrade ciprofloxacin under the simulated sunlight irradiation. Therefore, ZIF-8/ZnIn-LDOs nanocomposites have an important application prospect in photocatalytic degradation of pollutants.